NIX LEGEND: That Patrick Ewing has not been given an opportunity as an NBA head coach is an injustice, writes The Post’s Mike Vaccaro. Photo: AP

SAN ANTONIO — The fate of the Spurs’ championship aspirations rests fully on Tony Parker’s ailing right hamstring — which, Parker said yesterday, could give out at any time.

“The doctors say it will not change anything if I rest two more days,” Parker said after the Spurs practiced yesterday in preparation for Game 5 of the NBA Finals tonight against the Heat. “My hamstring can tear any time now.

“So, if it was the regular season, I would be resting, like, 10 days. But now it’s the NBA Finals … if it gets a tear, it’s life.”

Parker injured his hamstring in the Spurs humiliation of the defending champion Heat in Game 3 of the Finals on Tuesday, leaving his status for Game 4 up in the air until the morning of the game. But after declaring he would play, Parker looked like his usual self in the first half, scoring 15 points and dishing out six assists.

But Parker went on to miss all four of his shots after halftime, and he admitted after the Heat won 109-93 to even the series at two games apiece he was fatigued in the second half. But with two days off between Games 4 and 5, Parker said he hoped he would be able to give a full effort when the two teams take the floor tonight.

“It feels good,” he said. “I feel like I’m getting stronger with it. My goal is to be close to 100 percent by [tonight]. I felt confident being disciplined with all the treatments [and] with the ice right now.

“Hopefully I’ll be good [tonight].”

Although the final score of Game 4 made it look like a comfortable Heat victory, it actually was a back-and-forth affair through the first three quarters, despite all of the firepower LeBron James, Dwyane Wade and Chris Bosh — who combined to score 85 of Miami’s 109 points — were throwing at San Antonio.

But after the Spurs committed 19 turnovers and shot 44 percent — while allowing Miami to shoot over 50 percent at the other end — Parker admitted regardless of what the Heat do, San Antonio simply has to play better in tonight’s Game 5.

“Bottom line, you just have to play better,” he said, “and we have to play better. Miami stepped up big. Their Big Three played great, and you have to give them a lot of credit. You can’t win if you’re going to have [19] turnovers and make too many mistakes against a team like that.

“We have to understand that their identity is to play aggressive defense, and they gamble and they’re going to take a lot of chances with steals and blocks. We just have to be smarter with our decisions.”

Because of the way the Finals schedule breaks down, with one team getting the three middle games of the best-of-seven series at home, if the Spurs lose tonight on their home floor they’ll find themselves having to win both Game 6 and 7 on Miami’s home floor.

That’s why Tim Duncan, who is searching for his fifth ring, said tonight’s game is a must-win.

“We don’t want to go back down there down a game with two games remaining at their house,” he said. “It is a must-win situation. Obviously we lose this game … we’re not giving up or anything, but we want to go back up [and] with a chance to finish there.

“[There’s] huge pressure if we have to go back there and try to win two.”